1. Field of the Invention
The present invention relates generally to a flight system and a system for forming virtual images for an aircraft. More specifically, the invention relates to a system for providing the virtual images, which is artificially generated, to a pilot in order to facilitate the operation of a rotor craft or a light fixed wing aircraft.
2. Description of the Prior Art
Currently, rotor crafts, such as helicopters, are widely used for saving a life in the sea or a mountainous area, for transporting an emergency patient, for transporting goods to a mountain hut and so forth in all over the world.
The rotor crafts have advantages of requiring only a small area for takeoff and landing and of being capable of hovering, so that the rotor craft is an ideal transportation, which can fly anywhere anytime in theory. However, there is a problem in that the rotor crafts can not fly even in slightly bad weather, such as a fog and a light rain. In addition, recently, the rotor crafts are scarcely used for transporting persons although there are some experimental operation cases as rotor crafts on company business. Moreover, the rotor crafts can not fly when it is raining lightly.
The reasons why the reliability of such a rotor crafts are low, are the following reasons (1) through (5).
(1) As shown in FIG. 11, there are some cases where the instrument flight rules (which will be hereinafter referred to as "IFR") can not be utilized. In the IFR, a radio guidance system, such as a radar, utilizes an inertial navigation system to allow an aircraft to fly in accordance with the direction of an air traffic controller so that the aircraft can fly when there is no visibility. The control policy is to insure safety by assigning an exclusive space to the respective aircraft. Since the respective aircraft is in duty bound to fly in the assigned space, the flight path 1 can not be suitably changed. Moreover, since automatic landing gears have been developed, an aircraft can take off and land unless it is considerably bad weather. Therefore, a scheduled service using a supercarrier equipped with such a landing gear has been accomplished a high on time departure rate of 98% or more. This is provided mainly for purpose of supporting the operation of a large fixed wing aircraft, and such an aircraft is in duty bound to fly via the sky of radio marks provided in a flight route.
However, the rules of FIG. 11 can not be utilized when the rotor crafts freely fly to utilize a heliport being one of a great many heliports, which are located in every place and which have no radio mark. In addition, the rules of FIG. 11 can not be utilized in an extra heliport for disaster and emergency.
(2) Moreover, radar waves for the IFR can be utilized for only places near large airports having radars. In addition, when the rotor crafts fly at a low altitude, there are some cases where the radar waves for the IFR can not utilized even near large airports since the radar waves are blocked by mountains. Therefore, the rotor craft often flies in accordance with the visual flight rules (VFR).
(3) Since the VFR needs severe conditions for weather, particularly for visibility, the rotor crafts are difficult to fly in the fog, rain and night, and the on time departure rate is relatively low, for example a level of 60%. These are the reasons why helicopters are not widely used. This has become a serious problem common to regular service as well as lifesaving, disaster support and so forth.
(4) The IFR is clearly distinguished from the VFR. However, actual weather changes in accordance with time, regions, altitude and so forth. For example, even if the VER allows a flight, weather often gets worse to approach to the instrument flight conditions.
As shown in FIG. 12, even if the sky is covered by cloud 2 or fog, there are often some visibility near the ground. In addition, when it is bad weather, the rotor crafts often fly in a flight path 3 at a low altitude to intend to fly below the cloud 2. On the other hand, if the rotor crafts can raise its flight altitude to fly in the cloud 2, it is impossible to use the visual flight rules although safety is improved.
Such circumstances on operation conditions can not be applied to a large fixed wing aircraft, which flies at a high altitude wherein it is always clear up and which has no obstacles except for other aircraft.
(5) In recent years, IFR utilizing a global positioning system (GPS). This IFR provides air traffic control rules, which improves safety by exchanging the positional information obtained by the GPS between the respective fixed wing aircraft and which has a higher degree of freedom. However, there is a problem that such air traffic control rules are bound by a preset flight plan, so that it is not possible to completely solve the problems on the flight safety. Therefore, it is possible to obtain only limited advantages in order to improve the reliability of a rotor craft.
In order to solve these problems, it is considered utilizing a simulation technique. A simulation technique, which is currently used for the development of aircraft, the pilot training and so forth, is widely applied to the field of amusements as a so-called virtual reality technique. In this technique, a three-dimensional digitized map, i.e., a virtual space, is prepared to be provided to a pilot as an image projected on a display, which is mounted on a helmet, or on a domed screen.
As will be described later, in this prior art, there are the following problems a through d in that it is not possible to faithfully reflect the actual situation which changes every moment.
a. Although it is required to artificially input an image, it is impossible to input all the actual situation on the ground since it takes a great deal of time.
b. Although it is required to inspect the image in comparison with the actual topography in order to insure safety, it also takes a great deal of time.
c. There is a problem that it is impossible to obtain a depth perception and a sense of speed if the image is simplified, so that there is a serious disadvantage in that the pilot does not notice that the aircraft approaches the ground.
d. The digital map published by the Geographical Survey Institute is a three-dimensional map information and has a high utility value. However, this digital map as well as all the above artificial maps are short of reality.
It is also considered utilizing rules for providing the pilot with an image obtained by a millimeter wave radar. Such rules sufficiently narrow beams of a millimeter wave radar to irradiate the narrowed beams in vertical and horizontal directions to form an image in the same manner as a manner for forming a screen of a television, and displays the image for the pilot. Since millimeter waves travel relatively far even in bad weather, the millimeter waves are suitable for a display unit in bad weather.
Unlike the above described artificial display system, since the pilot flies while observing the actual topography by means of radio waves, there is an advantage in that the pilot can observe the actual topography in real time. However, there are the following problems e through g in that it is possible to prepare an image having reality, which satisfies the pilot, by only millimeter waves.
e. Since the antenna of a millimeter wave radar is relatively large and heavy, it is not possible to irradiate beams of the millimeter wave radar in vertical and horizontal directions with a high frequency. Since the frequency is about 10 Hz at the highest, it is impossible to obtain an image changing every moment, such as a television picture, in theory (15000 Hz in television). Even if the number of scanning lines on a screen is about 50, which is about a tenth of that of television, the update rate is a few seconds, and the image seems to be an image obtained by changing still images every a few seconds. Therefore, this image can not be suitably used as a visual field image for a helicopter pilot.
In addition, since the wavelength of a millimeter wave is far longer than that of a light wave, the image is considerably faded even if it takes a sufficient time to iradiate the beams, so that it is too insufficient to form the pseudo field of vision.
f. Since it takes a lot of time to prepare an image by means of a computer, the prepared image is always a delayed image.
g. If the scanning angle range of the radar is reduced, the image is relatively sharp. However, if the pilot's field of vision is narrow, it is impossible for the pilot to safely operate the rotor craft to make a flight.